Re: Statistics updates is delayed when using `commit and chain`

On Mon, 12 Jul 2021 at 20:56, Lætitia Avrot <laetitia(dot)avrot(at)gmail(dot)com> wrote:

> Hello Japin,
>
> Thank you for the patch. I read it and I find myself with one question: why do we update statistics even though there was a rollback? I know that that was the behaviour before, but is it still worth it?
>

I test the following case, and found it also update the statistics even if we
rollback. So I update the statistics here. On the other hands, the insert tuple
rollbacked still in data block, so IMO we should update the statistics. I'm not
sure it is right.

postgres=# create table test (id serial, value text);
CREATE TABLE
postgres=# SELECT n_tup_ins FROM pg_stat_all_tables WHERE relname = 'test';
n_tup_ins
-----------
0
(1 row)

postgres=# BEGIN;
BEGIN
postgres=*# INSERT INTO test (value) VALUES ('bla');
INSERT 0 1
postgres=*# SELECT n_tup_ins FROM pg_stat_all_tables WHERE relname = 'test';
n_tup_ins
-----------
0
(1 row)

postgres=*# ABORT ;
ROLLBACK
postgres=# SELECT n_tup_ins FROM pg_stat_all_tables WHERE relname = 'test';
n_tup_ins
-----------
1
(1 row)

--
Regrads,
Japin Li.
ChengDu WenWu Information Technology Co.,Ltd.